Cholesteric liquid crystal displays (ChLCD's) have existed for several decades. ChLCD's are unique because of their “nonvolatile memory” characteristic; once an image is written to a display, the current image will remain indefinitely until a new image is written. ChLCD's can also be viewed in ambient light without back lighting. Both of these characteristics significantly reduce total power consumption when compared to other displays.
When many ChLCD's are refreshed or the displayed image is changed, the pixels are first driven to a uniform reflective state, then the new image is written to the display. This reflective state appears as a white flash to viewers.
There exists a need for a simple drive scheme that achieves gray scale reflection for passive matrix displays and eliminates the appearance of a white flash when a new image is written to a ChLCD.